Engines may include crankcase ventilation systems to vent gases out of the crankcase and into an engine intake manifold to provide continual evacuation of gases from inside the crankcase in order to reduce degradation of various engine components in the crankcase. The crankcase ventilation system may include a positive crankcase ventilation valve (PCV valve) for enabling one-way flow of crankcase gases from inside the crankcase to the intake manifold.
Crankcase ventilation systems may be intermittently diagnosed for PCV valve degradation. One example approach for PCV valve diagnostics is shown by Satou in US 2009/0211545. Therein, PCV valve degradation is determined based on air changes (e.g., changes to a throttle position) and fuel changes (e.g., fuel injection adjustments) required to maintain an idle speed as an opening of the PCV valve is adjusted. The opening of the PCV valve is, in turn, selected based on an air/fuel ratio of blow-by gas.
However, the inventors herein have recognized potential issues with such approaches. As one example, the blow-by based diagnostics approach may have significant noise issue due to various engine loads. These include, for example, engine friction, barometric pressure, AC compressor load, alternator load, etc. Consequently, computation intensive noise reduction algorithms may be required.
In one approach, to at least partially address these issues, a method for an engine crankcase ventilation system is provided. The method comprises controlling a fluid flow from a crankcase of an engine to an intake manifold of the engine via a positive crankcase ventilation valve, and in a first condition, indicating whether the positive crankcase valve is stuck open responsive to spinning the engine unfueled in a reverse direction, and in a second condition, indicating whether the positive crankcase valve is stuck closed responsive to spinning the engine fueled in a forward direction.
As one example, the method may further comprise indicating pressure in a crankcase ventilation tube via a pressure sensor, the crankcase ventilation tube fluidically coupling the crankcase to an air intake system configured to draw intake air into the engine. In the first condition, the method may include indicating the positive crankcase valve is stuck open responsive to an increase in pressure in the crankcase ventilation tube above a predetermined pressure change threshold as indicated via the pressure sensor.
In one example, the method may further comprise indicating an air/fuel ratio in the intake manifold of the engine via an intake air oxygen sensor, and in the second condition, indicating the positive crankcase valve is stuck closed responsive to the indicated air/fuel ratio less than a predetermined air/fuel ratio threshold. In this way, a positive crankcase valve may be diagnosed as to whether the positive crankcase valve is either stuck open or stuck closed. By periodically diagnosing the positive crankcase valve, engine complications due to a stuck open or closed positive crankcase valve may be reduced, or avoided.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.